The mapping class group power-quotient conjecture for hierarchically hyperbolic groups

Let SS be any surface of finite type, and let g1,,glMCG±(S)g_1,\dots,g_l\in \mathcal{MCG}^\pm(S). For a subgroup HH of a group GG, write H\langle\langle H\rangle\rangle for its normal closure. Power-quotient conjecture. There exists NN{0}N\in\mathbb{N}-\{0\} such that, for all K1,,KlZ{0}K_1,\dots,K_l\in \mathbb{Z}-\{0\},

MCG±(S)/{giKiN}\mathcal{MCG}^\pm(S)/\langle\langle \{g_i^{K_iN}\}\rangle\rangle

is hierarchically hyperbolic. The conjecture is open already for quotients by suitable powers of non-separating Dehn twists. It is motivated by the prospect that proving it would lead to a more complete theory of Dehn fillings for hierarchically hyperbolic groups.

Sources & referencesView supporting material

Primary source

Giorgio Mangioni and Alessandro Sisto, “Short hierarchically hyperbolic groups II: quotients and the Hopf property for Artin groups”, arXiv:2412.04364 (2025).

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